Johanna Bürger
A5039382401- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Planetary Science and Exploration
- Dark Matter and Cosmic Phenomena
- Astrophysics and Cosmic Phenomena
- Spacecraft and Cryogenic Technologies
- Scientific Research and Discoveries
- Atmospheric Ozone and Climate
- Radiation Therapy and Dosimetry
- Geomagnetism and Paleomagnetism Studies
- Ionosphere and magnetosphere dynamics
- Rocket and propulsion systems research
- Particle Detector Development and Performance
- Protein Structure and Dynamics
- Isotope Analysis in Ecology
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Quantum Electrodynamics and Casimir Effect
- Methane Hydrates and Related Phenomena
- Radioactivity and Radon Measurements
- Chemical Reactions and Isotopes
- Radioactive contamination and transfer
- Advanced Thermodynamics and Statistical Mechanics
- Radioactive Decay and Measurement Techniques
Massachusetts Institute of Technology
2000-2025
Technische Universität Braunschweig
2022-2024
RWTH Aachen University
2000
Fritz Haber Institute of the Max Planck Society
1996
Knowledge of the rigidity dependence boron to carbon flux ratio (B/C) is important in understanding propagation cosmic rays. The precise measurement B/C from 1.9 GV 2.6 TV, based on 2.3 million and 8.3 nuclei collected by AMS during first 5 years operation, presented. detailed variation with spectral index reported for time. does not show any significant structures contrast many ray models that require such at high rigidities. Remarkably, above 65 GV, well described a single power law R^{Δ}...
We present results over an 11-year Solar cycle of cosmic antiprotons based on <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mn>1.1</a:mn><a:mo>×</a:mo><a:msup><a:mn>10</a:mn><a:mn>6</a:mn></a:msup></a:math> events in the rigidity range from 1.00 to 41.9 GV. The <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mover accent="true"><c:mi>p</c:mi><c:mo stretchy="false">¯</c:mo></c:mover></c:math> fluxes exhibit distinct properties. magnitude...
We present the precision measurement from May 2011 to 2017 (79 Bartels rotations) of proton fluxes at rigidities 1 60 GV and helium 1.9 based on a total 1×10^{9} events collected with Alpha Magnetic Spectrometer aboard International Space Station. This is in solar cycle 24, which has maximum April 2014. observed that, below 40 GV, flux show nearly identical fine structures both time relative amplitude. The amplitudes decrease increasing rigidity vanish above GV. are reduced during period,...
We present high-statistics, precision measurements of the detailed time and energy dependence primary cosmic-ray electron flux positron over 79 Bartels rotations from May 2011 to 2017 in range 1 50 GeV. For first time, charge-sign dependent modulation during solar maximum has been investigated detail by leptons alone. Based on 23.5×10^{6} events, we report observation short-term structures timescale months coincident both flux. These are not visible e^{+}/e^{-} ratio. The across polarity...
A precision measurement of the nitrogen flux with rigidity (momentum per unit charge) from 2.2 GV to 3.3 TV based on 2.2×10^{6} events is presented. The detailed dependence spectral index presented for first time. rapidly hardens at high rigidities and becomes identical indices primary He, C, O cosmic rays above ∼700 GV. We observed that Φ_{N} can be as sum its component Φ_{N}^{P} secondary Φ_{N}^{S}, Φ_{N}=Φ_{N}^{P}+Φ_{N}^{S}, we found well described by weighted oxygen Φ_{O} (primary rays)...
We present the precision measurement of 2824 daily helium fluxes in cosmic rays from May 20, 2011 to October 29, 2019 rigidity interval 1.71 100 GV based on 7.6×10^{8} nuclei collected with Alpha Magnetic Spectrometer (AMS) aboard International Space Station. The flux and proton ratio exhibit variations multiple timescales. In nearly all time intervals 2014 2018, we observed recurrent a period 27 days. Shorter periods 9 days 13.5 are 2016. strength three periodicities changes rigidity....
We present the precision measurements of 11 years daily cosmic electron fluxes in rigidity interval from 1.00 to 41.9 GV based on 2.0×10^{8} electrons collected with Alpha Magnetic Spectrometer (AMS) aboard International Space Station. The exhibit variations multiple timescales. Recurrent flux periods 27 days, 13.5 and 9 days are observed. find that show distinctly different time proton fluxes. Remarkably, a hysteresis between is observed significance greater than 6σ at rigidities below 8.5...
We report the properties of precision time structures cosmic nuclei He, Li, Be, B, C, N, and O fluxes over an 11-year solar cycle from May 2011 to November 2022 in rigidity range 1.92 60.3 GV. The show similar but not identical variations with amplitudes decreasing increasing rigidity. In particular, below 3.64 GV B fluxes, 2.15 are significantly less affected by modulation than He flux. observe that these differences linearly correlated spectral indices fluxes. This shows, a...
Aims . This paper focuses on how insolation affects the nucleus of comet 67P/Churyumov-Gerasimenko over its current orbit. We aim to better understand thermal environment nucleus, in particular surface temperature variations, erosion, relationship with topography, and interior for location volatile species (H 2 O CO ). Methods have developed two models calculate subsurface temperatures 67P 6.45-year The first model, high resolution (300 000 facets), calculates temperatures, taking shadows...
We present the precision measurements of 11 years daily cosmic positron fluxes in rigidity range from 1.00 to 41.9 GV based on 3.4×10^{6} positrons collected with Alpha Magnetic Spectrometer (AMS) aboard International Space Station. The show distinctly different time variations electron at short and long timescales. A hysteresis between is observed a significance greater than 5σ rigidities below 8.5 GV. On contrary, proton similar variation. Remarkably, we found that are modulated more for 7...
Sufficient and necessary conditions for the occurrence of a Hopf bifurcation in chemical reaction mechanisms are presented using formalism stoichiometric networks. The applied to determine mechanistic basis oscillations isothermal surface reactions. Realistic examples given different oscillatory mechanisms.
ABSTRACT Optical properties are required for the correct understanding and modelling of protoplanetary debris discs. By assuming that comets most pristine bodies in Solar system, our goal is to derive optical constants real material. We determine complex index refraction near-surface material comet 67P/Churyumov–Gerasimenko by fitting sub-millimetre/millimetre observations thermal emission comet’s sub-surface made Microwave Instrument Rosetta Orbiter with synthetic temperatures derived from...
Abstract The microphysical structure of the lunar regolith provides information on geologic history Moon. We used remote sensing measurements thermal emission and a thermophysical model to determine properties regolith. expand upon previous investigations by developing model, which more directly simulates properties, such as grain size volume filling factor. modeled temperatures are matched with surface measured Diviner Lunar Radiometer Experiment board Reconnaissance Orbiter. maria...
We investigate the ability of a simultaneous fitting comet 67P/Churyumov-Gerasimenko's non-gravitational forces, torques, and total water-outgassing rate, as observed by Rosetta, to constrain complex thermophysical models cometary material. extend previous work geographically defined surface outgassing Rosetta observations testing effects more detailed geomorphological mapping, resolution shape-model used, self-heating neighbouring facets on shape-model, thermal inertia in solution,...
Understanding cometary activity gives us an insight into the materials properties, and therefore formation evolution processes of these relatively pristine protoplanetary objects. We will present results International Space Science Institute project to investigate phenomenon through effects outgassing on orbit spin-state comet 67P/Churymov-Gerasimenko, e.g. its non-gravitational dynamics. This Team gathered experts in orbital dynamics trajectory reconstruction together with thermophysical...
IntroductionThe Moon has many permanently shadowed regions (PSRs) inside of craters at the poles, which are only illuminated by indirect (reflected) sunlight and thermal radiation because small solar incidence angle obliquity. That is why terrain poles strongly influences temperature profile regolith. These exceptionally cold PSRs areas that most likely to harbor water ice (Vasavada 1999; Watson et al. 1961) therefore interest future landing missions. One example NASA CLPS-10, carries...
We investigate the ability of a simultaneous fitting comet 67P/Churyumov-Gerasimenko's non-gravitational forces, torques and total water-outgassing rate, as observed by Rosetta, to constrain complex thermophysical models cometary material. extend previous work geographically defined surface outgassing Rosetta observations testing effects more detailed geomorphological mapping, resolution shape-model used, self-heating neighbouring facets on shape-model, thermal inertia in solution, variation...
IntroductionOptical properties are required information for correct models of the early solar system and protoplanetary disks. To this day used in mostly provided by laboratory studies primitive analogs. Comets provide us with a closer analog to material but have been, until recently, difficult observe. Rosetta has given unique opportunity observe unprecedented accuracy.The Microwave Instrument Orbiter (MIRO) (Gulkis et al. 2007) measured thermal radiation emitted from subsurface comet...